Structure. Glycerol esters belong to the glycerolipids. Their structure consists of a glycerol backbone. One to three fatty acids are ester-linked to it. The number of fatty acids is reflected in the name of glycerol ester lipid classes: triglycerides contain three fatty acids, diglycerides two fatty acids, and monoglycerides one fatty acid.
Function. Glycerol esters are present in all living organisms where they serve a plentitude of functions. Their specific biological role often depends on the number of fatty acids. Glycerol esters with three fatty acids, triacylglycerols (TAG), may not be found in all prokaryotes but are the most prominent solution to store energy (and bioactive lipids) in all eukaryotes such as animals, plants, and fungi.
Diacylglycerols (DAG), glycerol esters with two fatty acids, act as key intermediates in the synthesis of phospholipids and other glycerolipids and function as second messengers in cellular signaling. Monoacylglycerols (MAG) too act as powerful signaling molecules in animals. They are required in the synthesis of the coating of the aerial surfaces of plants, and candidates for next-generation antibiotics.